Compared to say this? Which is CA legal if it has a bullet button and the lower reciever has always been a "pistol".

That's pushing the definition of a pistol, of course, but there is at least a functional definition to follow. From there, one can argue for against a ban based on the capability of the platform on its own merits. Does the danger of allowing laptop bag sized weapons capable of hitting targets at 300 yards at a pretty good rate of fire make such a weapon a public nuisance? I would think not, but I can listen to and weigh an argument to the contrary, as opposed to enduring braying about who would want such a thing or breathlessly repeated tales of incredibly rare deaths.

Prohibition of weapons

Good question from one point of view: the shorter the barrel, the shorter the range.

If a major point of a rifle is its effective range, why get a reduced-range short-barrelled rifle when you can get power and concealability with a sawed-off shotgun?

If power and range are what you want, just get a full-length rifle.

Isn't sawed off shotguns banned under the short barrel rifle? I guess I could google. Anyway the only purpose of a short barreled rifle I can think of is a poor pistol shooter that needs to do a job and still have a weapon handy.

The reason SBRs are illegal is that a SBR is easily concealed. You can build a carbine that has decent range, high capacity, and a rifle round (ie Armor piercing) that you can carry concealed.

You could easily carry this guy under a coat into a building and do quite a bit of damage. Now I don't agree with the law. But if you live outside of CA it really is just a matter of getting a $200 tax stamp inside of CA good luck.

SBR federal
Shoulder fired (This is important cause if you put a shoulder stock on a pistol it becomes a SBR)
barrel length of less than 16 inches or overall length of less than 26 inches

here is the law

27 CFR 478.11
Short-barreled rifle.
A rifle having one or more barrels less than 16 inches in length, and any
weapon made from a rifle, whether by alteration, modification, or
otherwise, if such weapon, as modified, has an overall length of less than
26 inches.

Short-barreled shotgun.
A shotgun having one or more barrels less than 18 inches in length, and
any weapon made from a shotgun, whether by alteration, modification, or
otherwise, if such weapon as modified has an overall length of less than
26 inches.

CA SBR is a little more strict as the Barrel has to be more than 16 inches and the overal lenght has to be more than 26 inches. Also if its center fire the over all length has to be more than 30 inches

here is the law as written note how CA has a
'Constructive possession' clause so
Do NOT get 'cute' and slip a buttstock on your AR pistol buffer tube.
Do NOT have shorty upper(s) unless you own legit pistol lower(s).
Do NOT own a buttstock if you only have an AR pistol but no AR rifle.

As used in Sections 16530 and 16640, Sections 17720 to 17730, inclusive,
Section 17740, Article 1 (commencing with Section 27500) of Chapter 4 of
Division 6 of Title 4, and Article 1 (commencing with Section 33210) of
Chapter 8 of Division 10 of Title 4, "short-barreled rifle" means any of
the following:
(a) A rifle having a barrel or barrels of less than 16 inches in length.
(b) A rifle with an overall length of less than 26 inches.
(c) Any weapon made from a rifle (whether by alteration, modification, or
otherwise) if that weapon, as modified, has an overall length of less than
26 inches or a barrel or barrels of less than 16 inches in length.
(d) Any device that may be readily restored to fire a fixed cartridge
which, when so restored, is a device defined in subdivisions (a) to (c),
inclusive.
(e) Any part, or combination of parts, designed and intended to convert a
device into a device defined in subdivisions (a) to (c), inclusive, or any
combination of parts from which a device defined in subdivisions (a) to
(c), inclusive, may be readily assembled if those parts are in the
possession or under the control of the same person.

shotguns
Penal Code 17180 Shotgun
As used in Sections 16530 and 16640, Sections 17720 to 17730, inclusive,
Section 17740, Article 1 (commencing with Section 27500) of Chapter 4 of
Division 6 of Title 4, and Article 1 (commencing with Section 33210) of
Chapter 8 of Division 10 of Title 4, "short-barreled shotgun" means any of
the following:
(a) A firearm that is designed or redesigned to fire a fixed shotgun shell
and has a barrel or barrels of less than 18 inches in length.
(b) A firearm that has an overall length of less than 26 inches and that
is designed or redesigned to fire a fixed shotgun shell.
(c) Any weapon made from a shotgun (whether by alteration, modification,
or otherwise) if that weapon, as modified, has an overall length of less
than 26 inches or a barrel or barrels of less than 18 inches in length.
(d) Any device that may be readily restored to fire a fixed shotgun shell
which, when so restored, is a device defined in subdivisions (a) to (c),
inclusive.
(e) Any part, or combination of parts, designed and intended to convert a
device into a device defined in subdivisions (a) to (c), inclusive, or any
combination of parts from which a device defined in subdivisions (a) to
(c), inclusive, can be readily assembled if those parts are in the
possession or under the control of the same person.